package com.shijie.utils;

import org.apache.commons.lang3.StringUtils;

import java.security.MessageDigest;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;

public class MD5Util {

    private static String byteArrayToHexString(byte b[]) {
        StringBuilder resultSb = new StringBuilder();
        for (byte aB : b) resultSb.append(byteToHexString(aB));
        return resultSb.toString();
    }

    private static String byteToHexString(byte b) {
        int n = b;
        if (n < 0)
            n += 256;
        int d1 = n / 16;
        int d2 = n % 16;
        return hexDigits[d1] + hexDigits[d2];
    }

    public static String MD5Encode(String origin, String charsetName) {
        String resultString = null;
        try {
            resultString = origin;
            MessageDigest md = MessageDigest.getInstance("MD5");
            if (charsetName == null || "".equals(charsetName)) {
                resultString = byteArrayToHexString(md.digest(resultString
                        .getBytes()));
            } else {
                resultString = byteArrayToHexString(md.digest(resultString
                        .getBytes(charsetName)));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return resultString;
    }

    private static final String hexDigits[] = {"0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};

    public static String createSignKey(SortedMap<String, String> headers, String sign) {
        Set<Map.Entry<String, String>> es = headers.entrySet();
        Iterator<Map.Entry<String, String>> it = es.iterator();
        StringBuilder sb = new StringBuilder();
        while (it.hasNext()) {
            Map.Entry<String, String> entry = it.next();
            String key = entry.getKey();
            String value = entry.getValue();
            if (!StringUtils.isEmpty(key)) {
                sb.append(key).append(value);
            }
        }
        return MD5Encode(sign + sb.toString() + sign, "UTF-8").toUpperCase();
    }
}
